[rbanffy]

Win SN8 at least they had the engine firing itself through the nozzle. This time it seemed the others failed to start.

Suicide burns are probably a very bad idea when they have crews and passengers anyway. I assume they'll fire up the landing engines sooner and leave enough time for the vacuum engines to fire as backups if needed.

[_Microft]

I think they will practice until they get the landing right all the time.

The engines with vacuum optimized nozzles are not suited for landing. They can not be gimbaled and are very over-expanded as well. I would not be surprised if the engines with vacuum nozzles destroyed themselves if they were fired at sea-level.

[rbanffy]

The engines were tested at sea level with the vacuum nozzle. Not being gimballed is bad, but they are throttleable, at least.

All these crazy failure modes will have to be tested before Starship is human rated.

[_Microft]

You are correct. There is even footage from a test on Youtube. Thanks for pointing this out.

[rbanffy]

You don't want them running for long on full power, but it's probably OK to use them for slowing down an emergency landing if the sea-level engines become otherwise unavailable. The alternative, as we (and SN10) saw with SN8 and SN9 is not great.

[numpad0]

Vacuum engines can’t be used at low altitudes, exhaust underexpansion cause flow to delaminate which will damage the nozzle which goes the way rocketry goes

[rbanffy]

They can't be used for long. The Raptor was test fired with the vacuum nozzle at sea level. Not perfect, but beats hitting the ground.